Morning Star Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morning Star Observatory clear sky chart from 2005-11-06 to 2024-01-13.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
42%
24043
21%
74371
12%
23987
52%
23987
24%
46892

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
24%
760
24%
2459
9%
757
43%
757
21%
1460
January11th to 20thNight
25%
732
23%
2378
10%
732
41%
732
20%
1479
January21st to endNight
23%
792
27%
2574
11%
792
43%
792
23%
1517
February1st to 10thNight
27%
720
23%
2246
10%
720
42%
720
25%
1364
February11th to 20thNight
17%
703
22%
2098
6%
699
34%
699
19%
1349
February21st to endNight
22%
592
23%
1776
8%
592
36%
592
19%
1175
March1st to 10thNight
26%
720
25%
2026
12%
720
38%
720
25%
1278
March11th to 20thNight
27%
720
19%
1980
7%
720
37%
720
21%
1322
March21st to endNight
27%
792
19%
2178
7%
792
37%
792
22%
1445
April1st to 10thNight
32%
720
23%
1980
9%
720
43%
720
28%
1211
April11th to 20thNight
35%
627
24%
1784
12%
627
46%
627
29%
1081
April21st to endNight
44%
540
26%
1620
16%
540
53%
540
32%
951
May1st to 10thNight
43%
540
17%
1620
7%
540
51%
540
27%
1034
May11th to 20thNight
45%
531
12%
1593
6%
531
49%
531
20%
1095
May21st to endNight
60%
582
16%
1744
11%
582
63%
582
26%
1138
June1st to 10thNight
58%
540
12%
1620
10%
540
60%
540
24%
1082
June11th to 20thNight
61%
540
13%
1620
10%
540
64%
540
27%
1060
June21st to endNight
67%
540
14%
1620
10%
540
69%
540
26%
1084
July1st to 10thNight
63%
525
10%
1575
8%
525
64%
525
20%
1141
July11th to 20thNight
70%
522
10%
1566
7%
522
71%
522
24%
1082
July21st to endNight
69%
591
13%
1672
11%
558
70%
558
23%
1170
August1st to 10thNight
62%
537
11%
1600
11%
534
62%
534
21%
1146
August11th to 20thNight
61%
534
15%
1598
13%
534
63%
534
20%
1149
August21st to endNight
61%
643
14%
1957
13%
643
62%
643
22%
1351
September1st to 10thNight
59%
720
18%
1980
14%
720
60%
720
26%
1326
September11th to 20thNight
52%
720
18%
1980
15%
720
55%
720
24%
1386
September21st to endNight
50%
720
23%
1980
16%
720
57%
720
29%
1281
October1st to 10thNight
49%
720
26%
2006
19%
720
56%
720
31%
1261
October11th to 20thNight
43%
720
28%
2160
19%
720
56%
720
30%
1289
October21st to endNight
47%
792
32%
2376
22%
792
61%
792
35%
1335
November1st to 10thNight
47%
740
27%
2297
19%
740
60%
740
30%
1323
November11th to 20thNight
40%
760
28%
2470
18%
760
53%
760
28%
1403
November21st to endNight
40%
760
27%
2470
16%
760
53%
760
26%
1424
December1st to 10thNight
32%
760
23%
2470
12%
760
47%
760
19%
1583
December11th to 20thNight
34%
759
27%
2914
14%
758
48%
758
24%
1601
December21st to endNight
30%
829
15%
4384
12%
817
42%
817
12%
2516

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
14%6%35%5%35%5%6%8%40%
74896
Night
15%6%25%4345%5%7%44%
74855
TransparencyDay
40%8%12%19%16%4
74619
Night
38%7%12%20%19%5%
74651
SeeingDay
18%13%22%23%16%8%
13926
Night
17%11%22%27%19%4
24053

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
16%6%2332335%7%50%
1706
11th to 20thDay
16%8%35%43433446%
1638
21st to endDay
14%6%24434445%51%
1782
February1st to 10thDay
16%5%25%444447%45%
1710
11th to 20thDay
19%6%34434445%44%
1748
21st to endDay
18%7%34446%5%45%41%
1480
March1st to 10thDay
14%5%2443445%6%49%
1934
11th to 20thDay
20%6%35%5%3445%7%39%
1980
21st to endDay
18%7%35%5%345%6%6%39%
2178
April1st to 10thDay
12%5%245%346%6%8%45%
1980
11th to 20thDay
15%5%346%3446%7%43%
2137
21st to endDay
13%4345%35%45%7%48%
2340
May1st to 10thDay
10%7%37%6%35%5%5%7%42%
2340
11th to 20thDay
16%6%36%6%45%6%6%7%34%
2301
21st to endDay
12%6%26%6%45%6%8%10%34%
2531
June1st to 10thDay
11%7%37%6%47%8%8%10%29%
2340
11th to 20thDay
8%5%26%7%5%6%7%9%10%34%
2340
21st to endDay
9%5%36%8%5%7%8%8%9%33%
2340
July1st to 10thDay
10%6%37%8%6%7%8%9%11%26%
2340
11th to 20thDay
11%448%8%5%8%8%8%10%25%
2340
21st to endDay
9%5%37%8%5%8%7%7%11%29%
2547
August1st to 10thDay
14%6%36%8%5%8%7%8%9%25%
2327
11th to 20thDay
14%6%36%7%5%6%6%9%10%28%
2303
21st to endDay
13%6%37%7%46%6%8%10%31%
2375
September1st to 10thDay
12%6%36%7%45%6%6%8%37%
1980
11th to 20thDay
18%6%36%6%46%5%6%8%34%
1980
21st to endDay
18%6%34435%45%7%41%
1980
October1st to 10thDay
16%6%24323347%50%
1954
11th to 20thDay
14%5%2322235%5%57%
1800
21st to endDay
15%424323345%56%
1980
November1st to 10thDay
12%423413345%58%
1778
11th to 20thDay
13%423424446%54%
1710
21st to endDay
15%5%2442345%6%52%
1710
December1st to 10thDay
18%7%26%6%34446%40%
1710
11th to 20thDay
16%5%14324347%51%
2153
21st to endDay
21%5%2332345%6%45%
3124
January1st to 10thNight
17%6%23324445%49%
2459
11th to 20thNight
17%6%34424446%45%
2378
21st to endNight
16%6%2442345%5%49%
2574
February1st to 10thNight
15%6%25%4335%45%49%
2246
11th to 20thNight
18%6%24424445%46%
2098
21st to endNight
17%6%35%4345%5%6%41%
1776
March1st to 10thNight
12%8%35%425%45%6%46%
2026
11th to 20thNight
17%7%26%4335%5%6%41%
1980
21st to endNight
18%5%35%5%2445%7%43%
2178
April1st to 10thNight
13%6%2342345%7%49%
1980
11th to 20thNight
15%6%34423346%51%
1784
21st to endNight
13%5%1432446%6%53%
1620
May1st to 10thNight
13%5%25%5%35%5%5%7%45%
1620
11th to 20thNight
15%6%37%5%45%45%7%39%
1592
21st to endNight
14%6%245%35%47%9%41%
1744
June1st to 10thNight
10%6%26%6%46%6%8%12%33%
1620
11th to 20thNight
10%5%26%5%35%7%6%11%41%
1620
21st to endNight
8%5%25%5%5%6%7%8%10%40%
1620
July1st to 10thNight
10%6%46%7%47%7%9%11%29%
1620
11th to 20thNight
8%5%35%6%45%8%9%13%32%
1620
21st to endNight
7%5%36%6%6%8%8%8%10%34%
1771
August1st to 10thNight
12%6%36%6%36%7%8%10%34%
1611
11th to 20thNight
13%7%36%6%46%6%6%10%33%
1598
21st to endNight
11%7%26%7%45%6%8%10%34%
1957
September1st to 10thNight
13%6%26%5%35%5%7%9%38%
1980
11th to 20thNight
18%7%36%6%3446%7%36%
1980
21st to endNight
18%6%245%24447%44%
1980
October1st to 10thNight
17%5%244135%45%49%
2006
11th to 20thNight
16%5%24423445%51%
2160
21st to endNight
15%313323345%57%
2376
November1st to 10thNight
14%423423335%56%
2297
11th to 20thNight
14%6%34323346%54%
2470
21st to endNight
15%5%243345%47%49%
2470
December1st to 10thNight
18%7%35%43445%6%41%
2470
11th to 20thNight
14%7%23424345%52%
3042
21st to endNight
22%7%2442446%6%40%
4532

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
36%5%9%23%21%6%
1707
11th to 20thDay
42%5%7%18%22%6%
1638
21st to endDay
36%37%23%23%8%
1782
February1st to 10thDay
40%5%10%20%19%6%
1710
11th to 20thDay
42%5%10%19%18%6%
1758
21st to endDay
46%6%7%15%17%9%
1480
March1st to 10thDay
36%48%21%22%8%
1934
11th to 20thDay
45%6%10%17%16%6%
1980
21st to endDay
44%6%12%20%15%3
2178
April1st to 10thDay
35%6%11%22%21%5%
1980
11th to 20thDay
38%6%9%19%21%7%
2137
21st to endDay
35%7%13%26%17%3
2340
May1st to 10thDay
39%9%14%20%16%3
2340
11th to 20thDay
45%11%13%18%11%2
2305
21st to endDay
41%10%15%22%11%1
2531
June1st to 10thDay
44%11%17%19%8%1
2340
11th to 20thDay
39%11%20%18%10%2
2340
21st to endDay
42%11%17%17%11%2
2340
July1st to 10thDay
47%13%16%15%8%2
2275
11th to 20thDay
46%12%20%13%7%1
2271
21st to endDay
42%14%19%17%8%1
2405
August1st to 10thDay
49%12%17%17%5%
2314
11th to 20thDay
46%13%16%16%7%1
2303
21st to endDay
44%11%17%18%7%2
2375
September1st to 10thDay
41%10%12%18%15%3
1980
11th to 20thDay
45%8%10%18%16%2
1980
21st to endDay
42%6%10%19%16%6%
1980
October1st to 10thDay
36%5%10%19%25%6%
1954
11th to 20thDay
30%410%24%23%9%
1800
21st to endDay
32%37%21%26%10%
1980
November1st to 10thDay
30%38%20%29%10%
1778
11th to 20thDay
32%5%6%23%27%8%
1710
21st to endDay
33%5%7%22%26%6%
1710
December1st to 10thDay
46%6%6%20%16%6%
1710
11th to 20thDay
34%29%19%26%9%
2150
21st to endDay
39%49%21%23%4
3124
January1st to 10thNight
37%411%19%23%6%
2459
11th to 20thNight
39%6%10%17%23%5%
2378
21st to endNight
36%46%22%26%6%
2574
February1st to 10thNight
37%411%21%20%6%
2246
11th to 20thNight
41%6%7%19%22%6%
2099
21st to endNight
43%7%8%16%19%7%
1776
March1st to 10thNight
37%5%9%17%22%9%
2026
11th to 20thNight
41%7%11%18%18%5%
1980
21st to endNight
42%5%10%22%18%3
2178
April1st to 10thNight
34%5%11%21%25%4
1980
11th to 20thNight
34%5%10%23%21%6%
1784
21st to endNight
33%5%14%26%19%3
1620
May1st to 10thNight
36%9%15%23%16%2
1620
11th to 20thNight
43%10%15%19%13%1
1593
21st to endNight
38%10%16%26%10%1
1745
June1st to 10thNight
39%11%20%21%7%1
1620
11th to 20thNight
36%11%22%22%9%1
1620
21st to endNight
36%13%19%17%12%4
1620
July1st to 10thNight
44%13%19%13%9%1
1575
11th to 20thNight
38%14%25%14%6%2
1566
21st to endNight
38%16%19%19%7%1
1672
August1st to 10thNight
43%14%19%18%7%
1600
11th to 20thNight
44%13%19%13%10%1
1598
21st to endNight
42%11%19%20%6%2
1957
September1st to 10thNight
39%9%14%22%13%3
1980
11th to 20thNight
45%8%13%18%15%2
1980
21st to endNight
39%6%10%22%19%4
1980
October1st to 10thNight
37%5%11%19%24%4
2006
11th to 20thNight
35%5%8%23%21%8%
2160
21st to endNight
30%37%21%28%10%
2376
November1st to 10thNight
33%48%19%25%10%
2297
11th to 20thNight
34%46%19%27%11%
2470
21st to endNight
35%47%22%25%6%
2470
December1st to 10thNight
42%6%9%19%19%6%
2470
11th to 20thNight
34%410%17%28%7%
3044
21st to endNight
43%411%17%21%4
4532

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
25%24%39%9%3
270
11th to 20thDay
25%24%29%17%5%
246
21st to endDay
22%29%35%12%3
264
February1st to 10thDay
23%30%34%12%2
240
11th to 20thDay
38%28%26%8%
240
21st to endDay
30%26%31%11%2
198
March1st to 10thDay
19%28%30%16%7%
374
11th to 20thDay
27%21%28%17%5%1
420
21st to endDay
24%21%29%20%6%
462
April1st to 10thDay
19%22%27%22%9%
420
11th to 20thDay
17%20%27%21%13%1
412
21st to endDay
21%12%29%22%12%5%
420
May1st to 10thDay
11%16%33%24%11%6%
423
11th to 20thDay
17%10%21%27%16%9%
447
21st to endDay
16%8%15%25%22%13%
485
June1st to 10thDay
13%7%16%32%20%13%
450
11th to 20thDay
11%5%19%22%27%15%
450
21st to endDay
12%417%33%21%14%
450
July1st to 10thDay
10%49%24%32%21%
445
11th to 20thDay
9%210%26%31%22%
444
21st to endDay
7%210%27%29%25%
488
August1st to 10thDay
19%311%26%19%21%
446
11th to 20thDay
14%39%29%26%19%
439
21st to endDay
16%212%25%29%17%
495
September1st to 10thDay
12%213%25%30%17%
450
11th to 20thDay
18%411%26%29%12%
450
21st to endDay
20%6%16%28%24%5%
450
October1st to 10thDay
23%7%15%26%20%8%
450
11th to 20thDay
15%13%26%27%15%4
450
21st to endDay
22%9%23%28%14%3
495
November1st to 10thDay
22%13%26%25%11%3
376
11th to 20thDay
17%23%34%18%7%1
270
21st to endDay
15%22%35%20%7%1
270
December1st to 10thDay
26%23%33%16%3
270
11th to 20thDay
21%18%36%18%7%
270
21st to endDay
24%21%35%14%5%1
297
January1st to 10thNight
20%23%28%23%6%
760
11th to 20thNight
18%20%31%26%5%
732
21st to endNight
17%21%34%25%3
792
February1st to 10thNight
18%16%34%27%5%
720
11th to 20thNight
22%22%36%18%1
703
21st to endNight
18%22%35%22%3
592
March1st to 10thNight
18%21%31%27%4
720
11th to 20thNight
22%16%30%23%7%1
720
21st to endNight
19%17%31%26%7%1
792
April1st to 10thNight
17%16%32%26%9%
720
11th to 20thNight
19%14%26%26%14%1
627
21st to endNight
14%10%27%32%16%1
540
May1st to 10thNight
13%9%26%33%18%1
540
11th to 20thNight
17%7%17%33%23%2
531
21st to endNight
14%311%28%34%8%
584
June1st to 10thNight
11%113%34%35%5%
540
11th to 20thNight
11%313%27%34%11%
540
21st to endNight
8%211%33%39%7%
540
July1st to 10thNight
12%27%24%43%11%
525
11th to 20thNight
9%16%24%48%13%
522
21st to endNight
8%17%25%46%12%
591
August1st to 10thNight
16%26%22%43%10%
537
11th to 20thNight
15%37%24%42%9%
534
21st to endNight
15%27%23%42%11%
643
September1st to 10thNight
13%49%27%38%8%
720
11th to 20thNight
19%411%25%34%7%
720
21st to endNight
20%416%30%27%3
720
October1st to 10thNight
18%8%17%23%25%8%
720
11th to 20thNight
19%9%23%29%18%3
720
21st to endNight
17%9%22%32%16%3
792
November1st to 10thNight
17%9%21%32%18%3
740
11th to 20thNight
17%14%24%32%12%1
760
21st to endNight
15%16%25%29%14%1
760
December1st to 10thNight
21%17%24%29%7%1
760
11th to 20thNight
18%11%32%32%7%1
760
21st to endNight
25%14%25%29%6%
836
Page generated at 2024-01-10 10:16:09. Version ac07

Copyright 2024 Attilla Danko


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